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Microsoft Security Bulletin (MS00-086)
Patch Available for "Web Server File Request Parsing" Vulnerability
Originally posted: November 06, 2000
Microsoft has released a patch that eliminates a serious security
vulnerability in Microsoft(r) Internet Information Services 5.0. The
vulnerability could enable a malicious user to run operating system
commands on an affected web server.
Microsoft strongly urges all customers using IIS 5.0 to apply the
patch immediately. IIS 4.0 is not affected by the vulnerability.
Frequently asked questions regarding this vulnerability and the patch
can be found at
When IIS receives a valid request for an executable file, it passes
the name of the requested file to the underlying operating system
for processing. However, due to an implementation flaw in IIS 5.0, it
is possible to create a specially-malformed file request that
contains both a file name and one or more operating system commands.
Upon receiving such a request, IIS 5.0 would pass the entire string
to the operating system, which would first process the file and then
execute the commands. The file would need to reside in a folder to
which the user had execute permissions, but it would not necessarily
need to be an executable file.
The ability to execute operating system commands on the web server
would enable a malicious user to take virtually any action that an
interactively-logged on user could take. Although this would not give
the malicious user administrative control over the server, it would
nevertheless enable him to cause widespread damage. He could, for
instance, add, delete or change files on the server, run code that
was already on the server, or upload code of his choice and run it.
Microsoft strongly recommends that all customers running IIS 5.0
immediately apply the patch for this vulnerability. The patch also
eliminates the "Web Server Directory Traversal" vulnerability
discussed in Microsoft Security Bulletin MS00-078. IIS 4.0 is not
affected by the vulnerability, and IIS 4.0 customers do not need to
take any action.
Affected Software Versions
- Microsoft Internet Information Service 5.0
Note: IIS 4.0 is not affected by the vulnerability.
- Simplified Chinese:
- Traditional Chinese:
Note: This patch can be applied atop system running either Windows
2000 Gold or Service Pack 1. It will be included in Windows 2000
Service Pack 2.
Note: Additional security patches are available at the Microsoft
Please see the following references for more information related to
- Frequently Asked Questions: Microsoft Security Bulletin MS00-086,
- Microsoft Knowledge Base article Q277873 discusses this issue
and will be available soon.
- Microsoft TechNet Security web site,
Obtaining Support on this Issue
This is a fully supported patch. Information on contacting Microsoft
Product Support Services is available at
Microsoft thanks NSFocus (http://www.nsfocus.com) for reporting this
issue to us and working with us to protect customers.
- November 06, 2000: Bulletin Created.
THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED
"AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL
WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT
SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY
DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL,
CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF
MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION
OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES
SO THE FOREGOING LIMITATION MAY NOT APPLY.
Last Updated November 06, 2000
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